This moment, for instance:
I'd say that a crying child looking up at the butchered corpse of his mother would count as "frightening", or at the very least a serious and mature scene.
You'll never find anything even remotely close to this in Dragonflight.
You can fiind other grim scenes like this; such as the Forsaken mage torturing a civilian by turning him into a fish, while on land (another grim scene from Brennadam). Or the Proudmoore cadets using a troll prisoner as a literal training dummy. It's small details like this one that made BfA bearable, and you won't find anything like this in Disney Dragonflight.